Adjustable camshafts for internal combustion engines having a support shaft which extends in a rotational axis are known, and at least one cam pack is received on the support shaft such that it can be moved in the direction of the rotational axis. The cam pack corotates with the rotation of the support shaft, for which purpose a spline structure between the support shaft and the cam pack can serve, and a rotation of the cam pack on the support shaft is prevented by way of the spline structure. In order to latch the cam pack in discrete axial positions on the support shaft in reproducible axial positions, latching elements are known which can be prestressed by way of spring elements, and the latching elements can latch into latching element receptacles, as a result of which the axial position of the cam pack on the support shaft is defined. The different axial positions of the cam pack on the support shaft serve to bring different cam elements which the cam pack can have into connection with valves or tapping elements for actuating valves. The different cam elements can define different control times for opening and closing the valves of the internal combustion engine, or the valve stroke can be changed by way of different cam elements in operative connection with a tapping element or directly with a valve. Here, the change takes place by way of different, discrete axial positions of the cam pack being assumed on the support shaft, and the displacement of the cam pack takes place, for example, by way of a manipulation means which is received in a stationary manner in the cylinder head and can interact with an adjusting element which can likewise be included by the cam pack.
For example, DE 10 2010 011 897 A1 discloses an adjustable camshaft for an internal combustion engine having a support shaft which extends in a rotational axis, and a cam pack is received on the support shaft such that it can be moved axially. A latching element in the form of a ball which is loaded by way of a spring force of a spring element serves to latch the cam pack in discrete axial positions. The ball can latch into different profile grooves as a result of the spring force, and the profile grooves are arranged with regard to the axial position in such a way that each profile groove corresponds to the contact of an associated cam track of a cam element against a tapping element.
The latching element and the spring element for loading the latching element with force are arranged in a receiving bore of the camshaft, the latching element receptacles being made on the inner side in the cam pack in the form of the profile grooves. If the camshaft has to be assembled, first of all the spring element has to be inserted into the receiving bore in the camshaft, and subsequently the latching element has to be inserted into the receiving bore counter to the spring force before the cam pack is arranged on the support shaft. When the cam pack is subsequently pushed on, the difficulty arises that the latching element has to be pressed into the receiving bore counter to the spring force of the spring element, in order to prevent blocking of the cam pack when being pushed onto the support shaft by way of the spherical latching element.
Furthermore, the disadvantage arises that, when the spring element or the latching element is not installed in a positionally correct manner during mounting of the cam pack on the support shaft or when the latching element or the spring element are mislaid, this error is discovered only during final control of the camshaft. Here, a rectification is disadvantageously not possible without complete dismantling of the camshaft.
It is additionally to be ensured during the production of the bores in the support shaft that there is a sufficient clearance from the adjacent spline structure, in order that no distortion of the receiving bore for receiving the spring element and the latching element occurs during possible subsequent hardening of the support shaft or surface finishing. As a result, the lack of freedom of movement of the latching element and the spring element would impair the latching action.